Dimitrov, who has never got beyond the third round in Paris, had been expecting to face experienced Viktor Troicki.

However, just minutes before he was due to go on court, Troicki withdrew with a back injury, allowing world number 182 Safwat to make his Grand Slam debut. In the process, he became the first Egyptian since Tamer El Sawy at the 1996 US Open to feature in a major.

"I was warming up and my coach said, 'hey look' and we saw up on the board that I was playing a different opponent," said 27-year-old Dimitrov, a former Wimbledon semi-finalist.

"I didn't expect that."

Dimitrov took advantage of a nervous start in the first two sets by Safwat who has won just one top-level match all year.

The Bulgarian was 3-0 up in the first and 4-0 in the second set to build a foundation for victory.

Safwat needed treatment for blisters on his right hand before putting up solid resistance in the third set before Dimitrov raced through the tiebreaker.

Dimitrov faces either Jared Donaldson of the United States or Chile's Nicolas Jarry for a place in the last 32.